The death of Fazul Abdullah Mohammed, mastermind of the deadly Kenya and Tanzania embassy attacks, is said to be a major disruption of Al Qaeda's efforts in the Horn of Africa.

Reporting from Washington — Al Qaeda's longest-serving and most senior operative in East Africa has been confirmed dead in Somalia, adding to the leadership vacuum in the global terror organization since the killing of Osama bin Laden last month.

The death in Mogadishu of Fazul Abdullah Mohammed, the mastermind of the 1998 bombings of U.S. Embassies in Tanzania and Kenya, is a major disruption of Al Qaeda's efforts to expand its hold on havens in the Horn of Africa, U.S. officials and counter-terrorism experts said Saturday.

No leader of Al Qaeda has emerged since Navy SEALs shot and killed the world's most-wanted terrorist. Ayman Zawahiri, long reputed to be Bin Laden's chief deputy, released a video last week condemning Bin Laden's slaying, but he did not make a clear announcement about taking control of the group.

"It's been a bad spring for Al Qaeda," said Bruce Riedel, a former CIA officer and currently a senior fellow at the Brookings Institution's Saban Center for Middle East Policy, a Washington-based think tank.

Senior members of the Obama administration, including Secretary of State Hillary Rodham Clinton and White House counter-terrorism chief John Brennan, were quick to trumpet the killing of one of Al Qaeda's most important — if lesser-known — operatives in what seemed to be an attempt to reclaim some of the public accolades the White House received in the days after the Bin Laden killing.

President Obama's approval ratings softened in recent weeks on economic news, down from the highs after the death of Bin Laden, polls have shown.

Mohammed, an East African by birth, was crucial in bringing such groups as the extremist Shabab in Somalia into the Al Qaeda fold, as well as attracting militant movements from other parts of Africa.

He also was a key link between militants in Africa and Al Qaeda's most dangerous affiliate, Al Qaeda in the Arabian Peninsula, based in Yemen, immediately across the Gulf of Aden from Somalia.

In recent weeks, violent protests in Yemen have continued to weaken the hold of the U.S.-allied government there. In May, local Islamic militants captured the southern port of Zinjibar.

U.S. intelligence officials are concerned that the Al Qaeda affiliate in Yemen will be able to operate more freely as the government loses control of more of the country.

In early May, U.S. forces in Yemen fired a missile from a drone aircraft targeting one of the Al Qaeda affiliate's most influential leaders, American-born Anwar Awlaki. He has been linked to active plots against the United States, including mail-bomb packages targeting cargo planes heading to the U.S. in October and the disrupted plot to blow up a Detroit-bound airliner on Christmas Day 2009.

Somali security forces did not immediately identify Mohammed when he was killed during a shootout Tuesday at a checkpoint northwest of Mogadishu. His identity was not confirmed until Saturday.

A Kenyan national, Mohammed had expert computer skills and a preference for baseball caps, according to a State Department report.

Counter-terrorism chief Brennan said in a statement Saturday that Mohammed's death was a "huge setback" for Al Qaeda.

"It is a just end for a terrorist who brought so much death and pain to so many innocents," Clinton said in a statement released during a visit to Tanzania on Saturday.

The 1998 bombings of the U.S. Embassies in Nairobi and Dar es Salaam killed 224 people, including 12 Americans, and injured more than 5,000 people.

The State Department had offered a $5-million reward for information leading to Mohammed.

White House officials praised the Somali transitional government's security forces for killing Mohammed. The weak, United Nations-backed administration is trying to bring stability to a country that hasn't been run by a central government since 1991.

A suicide bomber killed the Somali interior minister last week. Shabab claimed responsibility for that attack.

Shabab has been at the forefront of radicalizing and recruiting first- and second-generation Somali Americans to join the fight against the Somali government.

Over the last 10 years, Al Qaeda has placed "great emphasis" on expanding its operations into ungoverned regions of East Africa, said Frank Cilluffo, director of the Homeland Security Policy Institute at George Washington University.

"Mohammed found ways to take those [militant groups] with more nationalist regional aims and pull them into the broader global jihad," Cilluffo said.

In East Africa, Al Qaeda will have trouble finding a leader with Mohammed's standing and savvy, said Rick Nelson, a counter-terrorism expert at the Center for Strategic and International Studies, a Washington-based think tank.

"He will be replaced, but not by another individual with his type of experience and his competence," Nelson said.

There is no indication that information taken from the Bin Laden compound in Abbottabad, Pakistan, led to the shootout in Somalia that killed Mohammed.

"It's not a bad thing to be lucky every once in a while," said Nelson.